A series of supports functionalized with different alkyl chains and covered with magnetite were synthesized, characterized and applied in the sample pre-concentration of four non-steroidal anti-inflammatory drugs (acetaminophen, naproxen, diclofenac and ibuprofen) contained in wastewater samples. The general methodology involved magnetic solid phase dispersion followed by the analysis by high-performance liquid chromatography with ultraviolet detection. The magnetic supports were initially dispersed in the samples with the aid of Triton X-100, then supports were magnetically isolated and the analytes were eluted with methanol. Finally the extract was injected into the HPLC system. The highest recovery percentage (>90%) was obtained with the support containing octyl chains (C8) at pH 3. The lowest limits of detection achieved ranged within 12 ?g L?1 with repeatability (expressed as RSD) below 5% in all cases. The method was applied in the analysis of wastewater samples.